CN109039464A - A kind of microwave photon millimeter wave ultra-wideband signal generating method and device based on up-conversion - Google Patents

Abstract

A microwave photonic millimeter wave ultra-wideband signal generation method and device based on up-conversion, belonging to the technical field of microwave photonics. Composed of laser source, polarization controller, arbitrary waveform generator, microwave signal source, dual parallel Mach-Zehnder modulator, erbium-doped fiber amplifier, optical isolator, first circulator, single-mode fiber, second circulator, photoelectric detection device and spectrum analyzer. The present invention generates a millimeter-wave ultra-wideband signal at 22GHz-29GHz based on the up-conversion technology, and the up-conversion realized by single-sideband modulation can overcome the dispersion effect in the single-mode optical fiber, so that the generated ultra-wideband signal can be transmitted over a long distance; The double Brillouin scattering effect realizes single sideband modulation, which has the characteristics of simple structure and easy implementation. Moreover, the amplification of the Brillouin gain and the attenuation characteristics of the loss make the spectrum of the generated ultra-wideband signal better meet the power spectral density mask specified by the Federal Communications Commission of the United States.

Description

A microwave photon millimeter wave ultra-wideband signal generation method based on up-conversion and its device

technical field

The invention belongs to the technical field of microwave photonics, and in particular relates to a method and device for generating a microwave photon millimeter wave ultra-wideband signal based on up-conversion.

Background technique

With the rapid development of wireless communication technology, various types of wireless communication systems have been developed one after another, and the available spectrum is increasingly saturated. However, people's requirements for wireless communication systems are still increasing, in order to achieve faster data transmission rates, lower costs, and lower power consumption. Under the background of such demand, UWB signal has attracted people's widespread attention, and has become a hot issue in the research and development of wireless communication. Due to its low power consumption, anti-multipath fading, no carrier and high data rate, ultra-wideband signals can be applied to short-distance large-capacity wireless communications and sensor networks, and are regarded as key factors in the field of next-generation wireless communications.

The traditional ultra-wideband generation method based on electrical domain signal processing is limited by the electronic bottleneck effect, unable to generate signals with a bandwidth of tens of GHz or even hundreds of GHz, and is susceptible to electromagnetic interference that shortens the transmission distance. Optical technology has the advantages of large bandwidth, high frequency, and low phase noise. By using microwave photonics technology to interact optical signals with electrical signals in the microwave band, stable and efficient ultra-wideband signals can be generated.

Contents of the invention

The purpose of the present invention is to provide a microwave photon millimeter wave ultra-wideband signal generation method and device based on up-conversion. The invention uses the secondary Brillouin effect to up-convert the ultra-wideband signal, so that the system structure is simple and easy to implement. Thanks to the selective amplification and attenuation characteristics of the Brillouin gain spectrum and loss spectrum, the generated UWB signal spectrum complies with the regulations of the U.S. Federal Communications Commission for UWB signals.

The structure of the microwave photonic millimeter wave ultra-broadband signal generation device based on up-conversion proposed by the present invention is shown in Figure 1. It consists of a laser source, a polarization controller, an arbitrary waveform generator, a microwave signal source, and dual-parallel Mach-Zehnder modulation. It consists of an erbium-doped fiber amplifier, an optical isolator, a first circulator, a single-mode fiber, a second circulator, a photodetector and a spectrum analyzer.

The continuous optical signal fc output by the laser source is input into the dual parallel Mach- _Zehnder modulator through the polarization controller. A polarization controller is used to align the polarization state of the incident light with the main axis of the dual parallel Mach-Zehnder modulator. The dual-parallel Mach-Zehnder modulator is a commercial device integrated on a single chip, consisting of the first sub-Mach-Zehnder modulator, the second sub-Mach-Zehnder modulator, and the third sub-Mach-Zehnder modulator; the first sub-Mach-Zehnder modulator The Zendel modulator and the second sub-Mach-Zehnder modulator are embedded as two sub-modulators on the two arms of the third mother Mach-Zehnder modulator, the first DC regulated power supply, the second DC regulated power supply, the second The three DC regulated power supplies respectively provide DC voltages for the first sub-Mach-Zehnder modulator, the second sub-Mach-Zehnder modulator, and the third female Mach-Zehnder modulator; by adjusting the first DC regulated power supply, the second DC The output voltages of the stabilized power supply and the third DC stabilized power supply change the three DC biases of the dual-parallel Mach-Zehnder modulator to control the working state of the dual-parallel Mach-Zehnder modulator. controlling the arbitrary waveform generator so that it sends out a series of electrical Gaussian pulses as electrical ultra-wideband signals, and then applying them to the first sub-Mach-Zehnder modulator as the electrical signal input of the first sub-Mach-Zehnder modulator, controlling the output voltage of the first DC stabilized power supply so that the first sub-Mach-Zehnder modulator works at the maximum transmission point; at the same time, applying the microwave signal whose frequency is equal to the Brillouin frequency shift f _B output by the microwave signal source to the first The second sub-Mach-Zehnder modulator controls the output power of the second DC stabilized power supply so that the second sub-Mach-Zehnder modulator works at the orthogonal transmission point; and then adjusts the output voltage of the third DC stabilized power supply to change The bias voltage of the third female Mach-Zehnder modulator produces an optical carrier carrying an electrical ultra-wideband signal and a series of sidebands with a frequency interval of f _B at the output of the dual-parallel Mach-Zehnder modulator, as shown in Figure 2 (a) shown. Usually, the 10dB bandwidth of the UWB signal is smaller than f _B , so the UWB signal attached to the optical carrier will not be affected by other sidebands. The optical carrier and the sideband with a frequency interval of f _B output by the dual-parallel Mach-Zehnder modulator are amplified by the erbium-doped fiber amplifier, and sent to the I port of the first circulator through the optical isolator. The function of the optical isolator is to ensure that the optical signal One-way transmission, then, the signal amplified by the erbium-doped fiber amplifier is output from the port II of the first circulator into the single-mode fiber, and this signal has two functions.

First, when the power of the optical carrier signal output by the port II of the first circulator exceeds the threshold value of stimulated Brillouin scattering in the single-mode fiber, a Stokes light propagating backward will be generated in the single-mode fiber, The frequency difference between the Stokes light and the light carrier is the Brillouin frequency shift f _B , so its frequency is f _c -f _B , as shown in Figure 2(b). In the stimulated Brillouin scattering effect, the power of the optical carrier used as the pump light will gradually be transferred to the counterpropagating Stokes light, so that the optical carrier in the modulated signal is attenuated to a large extent. At the same time, because the sidebands of each order of the modulated signal and the UWB signal carried on the optical carrier do not reach the threshold of stimulated Brillouin scattering, their amplitudes remain unchanged. The generated Stokes light with frequency f _c -f _B is input from port II and output from port III of the first circulator, and then input from port I and output from port II of the second circulator as a new pump Light is input into a single-mode fiber. This new pump signal interacts with the signal output from the port II of the first circulator to the forward transmission signal in the single-mode fiber to produce the second stimulated Brillouin scattering effect. _A gain spectrum at fc _{- 2fB} and _a loss spectrum at fc are simultaneously produced by this new pump light at frequency fc-fB _. The gain spectrum overlaps with the negative second-order sidebands in the modulated signal output from the optoisolator (Figure 2(a)), thereby amplifying the negative second-order sidebands. Similarly, the loss spectrum overlaps with the optical carrier in the modulated signal output by the optical isolator (Figure 2(a)), so the optical carrier is further attenuated, and the second attenuation suppresses the optical carrier low frequency components. Figure 2(c) shows the final result after the modulated signal output by the optical isolator is processed by the secondary Brillouin effect, that is, the negative second-order sidebands are amplified, while the remaining sidebands are relatively suppressed in the modulated signal. Subsequently, the signal processed by stimulated _{Brillouin scattering} is output from the port III of the second circulator, and then transmitted to the photodetector for photoelectric conversion. The negative second-order sidebands are beat, so that the frequency of the ultra-wideband signal is shifted to the high frequency direction by 2f _B , and finally the ultra-wideband signal in the millimeter wave band is obtained.

The device features described in the device of the present invention:

(1) Based on the up-conversion technology, the millimeter-wave ultra-wideband signal at 22GHz-29GHz is generated.

(2) The frequency up-conversion realized by single-sideband modulation can overcome the influence of dispersion in single-mode fiber, so that the generated ultra-wideband signal can be transmitted over long distances.

(3) The single sideband modulation is realized by using the secondary Brillouin scattering effect, which has the characteristics of simple structure and easy implementation. Moreover, the amplification of the Brillouin gain and the attenuation characteristics of the loss make the spectrum of the generated ultra-wideband signal better meet the power spectral density mask specified by the Federal Communications Commission of the United States.

Description of drawings

Figure 1: Microwave photonic millimeter wave ultra-wideband signal generation device based on up-conversion;

Figure 2: Spectrum processing diagram;

Figure 3: Spectrogram of a Gaussian sequence generated by an arbitrary waveform generator;

Figure 4: Spectrogram of the modulator signal;

Figure 5: Spectrogram of the reverse propagating Stokes light measured at port III of the first circulator;

Figure 6: Spectrogram of the SSB modulation signal produced by the quadratic Brillouin scattering effect;

Figure 7: Spectrogram of the generated mmWave UWB signal.

Detailed ways

Example 1:

The laser source is the TSL-510 tunable laser of Santec Company, the wavelength range of the laser is 1510nm～1630nm; the polarization controller is the three-ring polarization controller of Sichuan Ziguan Company; the dual parallel Mach-Zehnder modulator is the MX- LN-40-PFA-PFA, the bandwidth is 40GHz, the working optical wavelength is 1530nm~1580nm, the half-wave voltage of the first sub-Mach-Zehnder modulator and the second sub-Mach-Zehnder modulator is 4.6V, the third mother The half-wave voltage of the Mahder modulator is 9.1V; the microwave signal source is Agilent's microwave signal generator E8257D, and the output frequency range is 100kHz to 70GHz; the arbitrary waveform generator is Agilent's M8195A; the first DC stabilized power supply , the second DC stabilized power supply, and the third DC stabilized power supply are all GPS-4303C of GW Instek, and the output voltage range is adjustable from 1V to 20V; the erbium-doped fiber amplifier is WZEDFA-SO- P-S-0-1-2; the optical isolator of Fibot Optoelectronics Technology (Shenzhen) Co., Ltd., the isolation is greater than 40dB; the length of the single-mode fiber is 14km; the first circulator and the second circulator are Shenzhen Zhiyuan CIR-3-1550-900um-1m-FC/APC from Optical Communication Technology Company; the photodetector is PD-40-M from Optilab, with a bandwidth of 40GHz; the spectrum analyzer is N9010A from Agilent, and the bandwidth of the measurement signal range is 10Hz～26.5GHz.

After connecting the system, turn on the switch of the equipment to make all the equipment in working condition. The laser source outputs continuous light with a wavelength of 1549.58nm, which is sent to a dual-parallel Mach-Zehnder modulator through a polarization controller for modulation. A radio frequency signal is output from a microwave signal source, its frequency value is set equal to the Brillouin frequency shift of 10.875 GHz, and then the radio frequency signal is applied to the second sub-Mach-Zehnder modulator. Control the arbitrary waveform generator to output a 13Gb/s Gaussian pseudo-random bit sequence, its 10dB bandwidth is about 7GHz, and apply it to the first sub-Mach-Zehnder modulator as an ultra-wideband signal. Figure 3 shows the spectrum of an UWB signal generated by an arbitrary waveform generator. In order to obtain a modulated signal with an optimal optical carrier to modulation sideband ratio, the first sub-Mach-Zehnder modulator is biased at the maximum transmission point, and the second sub-Mach-Zehnder modulator is biased at the orthogonal transmission point. Therefore, set the first DC stabilized voltage source to 0V, and set the second DC stabilized voltage source to 9.1V. Then a zero phase difference is introduced between the first sub-Mach-Zehnder modulator and the second sub-Mach-Zehnder modulator, thus setting the third DC regulated source to 0V. Figure 4 shows the spectrum of the optical carrier carrying the UWB signal and the modulated signal without the UWB signal. As can be seen in the comparison of the dotted line with the solid line, the linewidth of the optical carrier is significantly wider, which indicates that the UWB signal is successfully carried by the optical carrier with little change in other sidebands. Then the modulation signal is input into the erbium-doped fiber amplifier, and the modulation signal is amplified by 10dB. It can be observed that only the optical carrier exceeds the threshold of stimulated Brillouin scattering in a 14 km single-mode fiber. The single-mode fiber is the medium used to generate the stimulated Brillouin scattering effect. After measurement, the stimulated Brillouin scattering critical power of the 14km single-mode fiber is 7.5dBm, and its Brillouin frequency shift is 10.875GHz. Figure 5 shows the spectrum of the backpropagating Stokes light produced by the stimulated Brillouin scattering effect in a 14 km single-mode fiber. The signal output by the erbium-doped fiber amplifier is input into the optical loop composed of the first circulator, the second circulator and a 14km single-mode fiber to produce the secondary stimulated Brillouin scattering effect. After selective amplification and attenuation by the stimulated Brillouin scattering effect, as shown by theoretical analysis, the negative second-order sidebands in the modulated signal are amplified and the carrier is suppressed. Figure 6 shows the spectrum of the SSB modulated signal produced by the stimulated Brillouin scattering effect. It can be observed that the magnitude of the negative second-order sideband increases by 20dB compared to other sidebands, and the carrier is submerged by the UWB signal. Due to the imbalance between the upper sideband and the lower sideband, the UWB signal carried by the carrier and the negative second-order sideband are beat by the photodetector, so that the UWB signal is up-converted to 21.75GHz. Measured by a spectrum analyzer, the output spectrum of the photodetector is shown in Figure 7. It can be found that the spectrum of the generated signal starts at 22GHz. The frequency components between 21.75 GHz and 22 GHz are suppressed by the loss spectrum, which is generated when the reverse Stokes light is used as the pump light. Although this changes the waveform of the UWB signal, in practical applications It will not affect the use of UWB signals. What's more, this property allows the spectrum of the generated signal to match well with the mask specified by the FCC. However, since the frequency measurement range using a spectrum analyzer is from 10 Hz to 26.5 GHz, the complete spectrum from 22 GHz to 29 GHz cannot be obtained. Nonetheless, based on the available data obtained, it is certain that the proposed scheme can successfully generate mmWave UWB signals that effectively comply with the mask specified by the US Federal Communications Commission.

Claims (3)

1. A microwave photon millimeter wave ultra-wideband signal generating device based on up-conversion, characterized in that: by laser source, polarization controller, arbitrary waveform generator, microwave signal source, double parallel Mach-Zehnder modulator, erbium-doped optical fiber Amplifier, optical isolator, first circulator, single-mode fiber, second circulator, photodetector and spectrum analyzer; dual parallel Mach-Zehnder modulator consists of first sub-Mach-Zehnder modulator, second sub-Mach The first sub-Mach-Zehnder modulator and the second sub-Mach-Zehnder modulator are embedded as two sub-modulators in the two sub-modulators of the third female Mach-Zehnder modulator. On the arm, the first DC stabilized power supply, the second DC stabilized power supply, and the third DC stabilized voltage supply are respectively the first sub-Mach-Zehnder modulator, the second sub-Mach-Zehnder modulator, and the third female Mach-Zehnder modulator. The modulator provides a DC voltage. 2. A microwave photon millimeter wave ultra-broadband signal generator based on up-conversion as claimed in claim 1, characterized in that: the laser source is TSL-510 tunable laser of Santec Company, and the wavelength range of the laser is 1510nm～1630nm The polarization controller is the three-ring polarization controller of Sichuan Ziguan Company; the dual parallel Mach-Zehnder modulator is the MX-LN-40-PFA-PFA of Photline Company, the bandwidth is 40GHz, and the working light wavelength is 1530nm～1580nm. Among them, the half-wave voltage of the first Mach-Zehnder modulator and the second Mach-Zehnder modulator is 4.6V, and the half-wave voltage of the third Mach-Zehnder modulator is 9.1V; the microwave signal source is a microwave signal from Agilent Generator E8257D, the output frequency range is 100kHz ~ 70GHz; the arbitrary waveform generator is Agilent's M8195A; the first DC regulated power supply, the second DC regulated power supply, and the third DC regulated power supply are GPS from GW Instek -4303C, the output voltage range is adjustable from 1V to 20V; the erbium-doped fiber amplifier is WZEDFA-SO-P-S-0-1-2 of Wuxi Zhongxing Optoelectronics Technology Company; the optical isolation of Feibot Optoelectronics Technology (Shenzhen) Co., Ltd. Circulator, the isolation is greater than 40dB; the length of the single-mode fiber is 14km; the first circulator and the second circulator are both CIR-3-1550-900um-1m-FC/APC of Shenzhen Zhiyuan Optical Communication Technology Company; photoelectric detection The device is PD-40-M from Optilab Company, with a bandwidth of 40GHz; the spectrum analyzer is N9010A from Agilent Company, and the bandwidth of the measurement signal range is 10Hz-26.5GHz. 3. A microwave photon millimeter wave ultra-broadband signal generation method based on frequency up-conversion, characterized in that: the continuous optical signal fc output by the laser source is input into the dual parallel Mach- _Zehnder modulator through the polarization controller, and the incident light The polarization state is aligned with the main axis of the dual parallel Mach-Zehnder modulator; the arbitrary waveform generator is controlled to send out a series of electrical Gaussian pulses as an electrical ultra-wideband signal, which is then applied to the first sub-Mach-Zehnder modulator Among them, it is used as the electrical signal input of the first sub-Mach-Zehnder modulator; the output voltage of the first DC stabilized power supply is controlled to make the first sub-Mach-Zehnder modulator work at the maximum transmission point; at the same time, the output of the microwave signal source A microwave signal with a frequency equal to the Brillouin frequency shift f _B is applied to the second sub-Mach-Zehnder modulator, and controls the output power of the second DC stabilized power supply, so that the second sub-Mach-Zehnder modulator works at the quadrature transmission point ; By adjusting the output voltage of the third DC stabilized power supply, changing the bias voltage of the third female Mach-Zehnder modulator, generating an optical carrier carrying an electrical ultra-wideband signal at the output of the dual-parallel Mach-Zehnder modulator and a series of sidebands whose frequency interval is f _B ; the optical carrier output by the dual parallel Mach-Zehnder modulator and the sidebands whose frequency interval is f _B are amplified by the erbium-doped fiber amplifier and sent to the first circulator through the optical isolator Ⅰ port, and then the signal amplified by the erbium-doped fiber amplifier is output from the Ⅱ port of the first circulator into the single-mode fiber; when the power of the optical carrier signal output from the Ⅱ port of the first circulator exceeds the single-mode fiber, a stimulated Brillouin When the scattering threshold is reached, a backpropagating Stokes light will be generated in the single-mode fiber. The frequency of this Stokes light is f _c -f _B . In the stimulated Brillouin scattering effect, as The power of the optical carrier of the pump light will be gradually transferred to the backpropagating Stokes light, which will greatly attenuate the optical carrier in the modulated signal; at the same time, because the sidebands of the modulated signal and the The UWB signals on the optical carrier do not reach the threshold of stimulated Brillouin scattering, and their amplitudes remain unchanged; the generated Stokes light with frequency f _c -f _B is input from the port II of the first circulator , Ⅲ port output, and then input from the Ⅰ port and Ⅱ port output of the second circulator, as a new pump light input into the single-mode fiber; this new pump signal is output from the Ⅱ port of the first circulator The second stimulated Brillouin scattering effect occurs in the signal interaction of the forward transmission into the single-mode fiber; the gain at f _c -2f _B is simultaneously generated by this new pump light at frequency f _c -f _B Spectrum and the loss spectrum at _fc , the gain spectrum overlaps with the negative second-order sideband in the modulation signal output by the optical isolator, thereby amplifying the negative second-order sideband; similarly, the loss spectrum and the output of the optical isolator The optical carrier in the modulated signal overlaps, so the optical carrier is further attenuated, and the low-frequency component in the optical carrier is suppressed to a large extent after the second attenuation; subsequently, the signal processed by stimulated Brillouin scattering is processed by the second The Ⅲ port output of the circulator is then transmitted to the photodetector for photoelectric conversion, the ultra-wideband signal attached to the carrier beats with the negative second-order sideband at f _c -2f _B , thus moving the frequency of the ultra-wideband signal to the high-frequency direction by 2f _B , and finally obtaining the ultra-wideband Broadband signal.